1. Field of the Invention
The invention relates to a processor for computing (operation), a virtual memory system, and a virtual storing method.
2. Description of the Related Art
Multiprocessor systems have been heretofore proposed as means for improving computing power of a system. In addition, in recent years, further miniaturization of the process realizes a chip multiprocessor system in which a plurality of processor cores is mounted on one chip.
The chip multiprocessor system generally adopts a structure of connecting a plurality of processors, a memory interface with an external memory, and an external device interface, to a system bus within the chip. The respective processors within the chip perform the processing while referring to and updating the data in the external memory through the memory interface.
It is known that the respective processors perform the processing in cooperation with each other while transferring data among the processors directly toward each local memory built in each of the processors through the system bus (for example, see “10.2 The Design and Implementation of a First-Generation CELL Processor” D. Pham et al., 2005 IEEE International Solid-State Circuits Conference (ISSCC)).
As mentioned above, the computing power of the chip can be enhanced according to the miniaturization of the process with a plurality of processor cores mounted on the chip. Physically and in view of a cost, however, it is not easy to improve the capacity and the bandwidth of each external memory which supplies data to each of the processor cores in proportion to the number of the processors.
When plural processor cores request access to the external memory at the same time, they will scramble for the limited memory bandwidth. This results in a dissatisfactory performance which falls short of expectations.
Further, the memory capacity usable by the respective processor cores is relatively decreased. The shortage of the memory capacity often hampers full utilization of the enhanced computing power.
These problems can occur not only in the multiprocessor system but also in a single processor system. The number of the transistors increases according to the miniaturization. The additional transistors can be utilized for the speed-up of the single processor core. The capacity and the bandwidth of the data, however, are difficult to increase accordingly.